Add bcheck for csrf-magic backdoor

[timoles]

BCheck to detect a csrf-magic backdoor.

References:

• The backdoor code
• Exploit Writeupe
• Real-world CVE due to the backdoor

BCheck Contributions

• [x] BCheck compiles and executes as expected
• [x] BCheck contains appropriate metadata (name, version, author, description and appropriate tags)
• [x] Only .bcheck files have been added or modified
• [x] BCheck is in the appropriate folder
• [x] PR contains single or limited number of BChecks (Multiple PRs are preferred)
• [x] BCheck attempts to minimize false positives

Example output for finding:

Overview

Request

Response

[Hannah-PortSwigger]

Thanks for the submission!

Does a valid response for this vulnerability always contain a 200 response code? If so, adding an additional clause to your if... then statement can mean that we can only perform the "expensive" regex match when necessary.